The present invention relates to vehicle positioning systems, and in particular to vehicle position systems using emitters positioned on the vehicle and with respect to each other so as to provide a simple and effective means of directing the vehicle into, out of, or through a small space.
Since ancient times, it has been recognized that the control of a ship during docking is a task that requires great skill of the ship's helmsman and crew. Such skill is required because of the many and varied factors that can influence the motion of a vessel on the water. Currents in the water, waves, and winds exert significant effects on vessels attempting to dock. Other factors include the condition of the vessel; the size and shape of the vessel's hull; the position of the helm on the vessel; the nature, number, and location of propulsion systems on the vessel; the size and configuration of the dock or slip used; and the amount and nature of involvement from other persons either on board or on shore. Larger vessels have considerable inertia, and thus compensation for all of these effects becomes progressively more difficult as the size of the ship increases. Also, the effect of many of these factors is increased due to the low water speed at which docking generally takes place. Failure to properly compensate for these multiple and changeable effects may result in a disastrous collision between the vessel and its dock. In particular, it may be recognized that even if the bow of the vessel is correctly pointed at its target docking location, if the overall alignment of the boat is incorrect with respect to the dock, the result may be that the stern of the vessel swings as the dock is reached, causing a collision between the dock and side of the vessel. This particular problem is a common cause of damage to both watercraft and dock facilities even today.
Problems in approaching a dock or slip are not experienced only by the largest ocean-going vessels. Such difficulties are also encountered with smaller boats and watercraft, especially those with limited maneuverability relative to their size, such as yachts, cruisers, and houseboats. To perhaps a lesser extent, such problems may even be experienced with small, maneuverable watercraft, such as fishing boats, ski boats, and personal watercraft. All such vessels are typically brought into position at their slips or docks by a single pilot, without the aid of on-shore spotters or complicated electronic guidance systems. A similar problem is faced by the operator of a smaller boat when attempting to align the boat with a submerged boat trailer used to haul the boat over land.
It may be seen that there are two critical components of the vessel's direction and orientation that are important during docking. The first is the position of the vessel's bow relative to its dock or slip during approach. Assuming that the docking is to take place in the forward direction, the bow of the vessel should be pointed toward the dock as the docking maneuver begins. The second critical component is the orientation of the vessel with respect to the bow. Both types of information are critical, since a failure to maintain alignment of the boat's stern may cause a crash even if the bow of the boat is perfectly oriented with respect to the dock, slip, or trailer. It will be recognized that considerable experience and skill are necessary to simultaneously maintain both the bow and stern of the vessel in position during docking. As the pilot turns his or her head in an attempt to gather information about the position of the ship's stern, he or she is distracted at a critical time, which may cause the bow of the ship to fall out of alignment. Even an experienced pilot may be unable to successfully guide a vessel into its dock or slip if, for example, an unexpected wind or current change were to occur at a critical moment.
It should also be recognized that many of the same issues faced during the docking of watercraft are also of concern during the parking of land vehicles, particularly segmented vehicles such as tractor trailers, within tightly enclosed spaces. The position of the nose of the vehicle, as well as the position and orientation of the rear or trailer portion of the vehicle, must be precisely controlled to make such parking maneuvers possible. Again, experience and skill are required on the part of the operator to successfully perform such maneuvers without assistance.
The prior art includes numerous attempts to address these sorts of difficulties, none of which are wholly practical and feasible for all purposes and applications. U.S. Pat. No. 5,285,204 to White teaches a guidance system to aid in the position of a car within a garage, drive-through service lane, loading dock, or the like. The system uses a laser outside the vehicle that is intended to strike a target on the front of the vehicle. The driver then steers the vehicle so as to maintain the laser on the target as the vehicle moves into position. While this simple method of alignment may be sufficient for some purposes, such a method lacks any capability for independently aligning the rear portion of the vehicle, which may be important for reasons as described above. The method would also be inadequate for the docking of watercraft, since the stern of such a vessel is, as already explained, subject to movement and rotation with respect to the bow from myriad forces acting on the vessel. This single laser system would provide the helmsman of such a vessel with no information whatsoever about the position and orientation of the vessel's stern.
U.S. Pat. No. 3,149,196 to Roth teaches another guidance system to aid in the parking of a car or other vehicle in a tightly enclosed space. Roth '196 teaches that a light mounted on the side of the vehicle shines against a target mirror, with the light then being reflected to the vehicle's driver. Thus Roth '196 teaches a system in which the positions of the emitter and sensor are reversed from that of White '204. The driver is able to align the vehicle by maintaining the appearance of the reflected light in the center of the mirror. This approach; which again relies upon a single illumination source, suffers from the same disadvantages and limitations as described above for White '204.
The prior art also includes numerous attempts to address the docking or movement of a vehicle or vessel that incorporate two or more optical emission devices. U.S. Pat. No. 5,343,295 to Lara et al., for example, teaches a system for the alignment of an electrically powered vehicle with its recharging station. The system incorporates two laser emitting diodes mounted on the vehicle. These beams cross at a distance in front of the electric vehicle that is equal to the distance at which the vehicle should be positioned from the recharging unit in order for recharging to take place. The vehicle's driver may thus drive toward the recharging unit with the beams activated, stopping at the point where the beams striking the recharging unit are directed to the same spot. This alignment technique, like the one-emitter system described above, is insufficient for many applications because it includes no means by which the rear or stern of a vessel may be separately aligned. In this case, both beams emanate from laser emitting diodes mounted on the front of the vehicle, and thus no information about the relative position and orientation of the rear of the vehicle is utilized in positioning the vehicle.
U.S. Pat. No. 6,486,798 to Rast teaches a system for preventing damage to the wings of an aircraft while taxing in tight spaces. An illumination source is attached to both wingtips. If light from the illumination sources strikes an object or surface that lies directly in front of the wingtip, that light is reflected back to the eyes of the aircraft's pilot, who can then turn or stop the aircraft to avoid a collision. Again, this system contains no means for separate alignment of the rear of the aircraft. Like the device taught by Lara et al. '295, this device includes two illumination sources, but neither of those illumination sources provide the operator with any information about the position or orientation of the rear of the craft. The purpose of the Lara et al. '295 device is to simply make the pilot aware of obstacles in the path of the aircraft's wings.
There are docking systems in use today that utilize multiple LIDAR (laser detection and ranging) units to aid in ship guidance. For example, U.S. Pat. No. 3,690,767 to Missio et al. teaches an optical docking system for large ocean-going vessels that utilizes LIDAR-type laser pulse range radar systems. Two pulse range radar systems are installed at the vessel's dock. The vessel itself has a reflector mounted at its bow and stern. The pulse range radar systems are each directed to one of the ship-mounted reflectors, and continuously track their position as the craft approaches the dock. The system continuously calculates and records the time of travel of the laser beam from the dock to the reflector and back to the dock. By continuously calculating and comparing these values for the bow and stern reflectors, one may calculate the distance and velocity of the ship's bow and stern independently. This information is displayed in numerical form on a computer screen accessible to the ship's captain, thus providing the captain with additional information to aid in the maneuver and docking of the vessel.
While the system of Missio et al. '767 does, unlike the previously discussed prior art, provide information about the position and velocity of the stern of a vessel independently from the bow of that same vessel, this system still suffers from significant limitations. The two pulse range radar devices necessary in order to make this system operable are quite complex and expensive. Two such devices would be necessary at each dock or slip where the vessel is to be moored. While the cost of such devices might be feasible when the docking vessel is a large, ocean-going vessel carrying a massive and valuable cargo, such a system could not be feasible when the pulse range radar devices represent a significant cost with respect to, and perhaps even greater than, the cost of the vessel itself. Such will generally be the case when considering most yachts, houseboats, and other smaller watercraft designed for personal use. In addition, some means must be implemented in connection with a LIDAR-type system such that each of the two pulse range radar devices track their respective reflectors on the vessel. Missio et al. '767 teaches that the radar devices must initially be aligned with the reflectors on the ship manually. This would of course require at least one operator on the shore in order to set the initial alignment. Thus this device would be impractical at any dock or slip facility that did not maintain permanent personnel for such purpose. Again, this would make this device impractical for most docks or slips used by all but the largest commercial vessels.
Finally, there are a number of docking systems in use today that do not utilize LIDAR techniques but that to some extent serve to automate or semi-automate the docking process. These integrated systems may involve GPS (global positioning system) satellite guidance, electromechanical guidance, and autopilot manipulation. Such systems may be fixed to the dock or mounted on a vessel. In any case, such systems are very expensive, and require considerable training and skill for operation due to their complexity. They are thus, like the LIDAR systems described above, impractical for many important applications, including the vast majority of watercraft intended for personal use.
What is desired then is an inexpensive, simple-to-operate system for the guidance of vessels into and out of a dock or slip that allows for simultaneously monitoring and control of not only the position of the bow of a vessel but also the position and orientation of its stern. Such a system would also be of utility in many other related applications, such as the movement of any sort of vehicle into, out of, and through tight or enclosed spaces. This desire is fulfilled, and the limitations of the prior art overcome, by the present invention as described below.